Such a catalyst system is known from e.g. J. Catalysis, Vol. 33, p. 83-90 (1974); J. Catalysis, Vol. 70, p. 364-374 (1981); J. Mol. catalysis, Vol. 15, p. 157-172 and 173-185; Bull. Jap. Petroleum Institute, Vol. 18 (2) p. 162-166 (1976); Bull. Chem. Soc. Japan, Vol. 50 (4), p. 998-1002 (1977); and Chemtech, Feb. 1986, p. 112-117.
In these publications research efforts are described aiming at improved olefin disproportionation selectivity by pretreatment of MoO.sub.3 /Al.sub.2 O.sub.3 catalyst systems. This pretreatment actually consisted of the insertion of large polarizable cations such as K, Cs, Rb and Tl or addition of other copromotors, e.g. cobalt oxide, into molybdenum oxides-alumina systems and/or calcination of the initially prepared impregnated alumina carrier at varying temperatures and under varying gas atmospheres.
Varying degrees of reduction with hydrogen gas at different reduction temperatures of molybdenum-alumina catalysts for the disproportionation of lower olefins, were tried to improve the disproportionation selectivity, such as that disclosed in Japanese Patent Publication No. 28768-1987 which discloses a process for the disproportion of olefins, in the presence of a catalyst prepared by reducing a molybdenum tri-oxide carrying solid composite, to such an extent that the amount of the oxygen atoms is between 2.9 and 2.2 gram atoms per gram atom of molybdenum.
On the other hand, more recent efforts to improve the selectivity of molybdenum-alumina catalysts were directed to activation by means of organo-metal derivatives, such as those disclosed in Japanese Patent Publication No. 83043-1987 and Russian Patent No. 1,264,973.
It will be appreciated that there is still a great current interest in molybdenum-alumina catalysts to be used in hydrocarbon chemistry, due to the wide range of reactions to which they can be applied, and that during the past several years extensive research efforts continued, however without providing any desired disproportionation catalyst system. Such a desired catalyst system has to meet the demands of modern industrial processes, one of which relates to disproportionation of more particularly higher olefins containing 6 to 60 carbon atoms, and during which the undesired dimerization and oligomerization are avoided as much as possible Such a desired industrial process for the preparation of relatively narrow band predetermined fractions of olefins, containing 18-24 carbon atoms, is mainly consisting of at least a double bond isomerization reaction and a disproportionation reaction.
Therefore there is still a need for an improved industrial disproportionation process. It is an object of the present invention to provide such a desired improved catalyst system for disproportionation of more particularly higher olefins.